Unknown Generics - c++

Question

I am attempting to create a database system modeling SQL, where each table is stored in a JSON file. Really not focusing on speed at the moment as this is more an exercise in communication. I came up with the following markup,
{
"table": {
"auto_increment": 3,
"last_edited": 1423163442
},
"definitions": [
{
"name": "id",
"kind": "INT",
"length": 8,
"default": "NONE",
"index": "PRIMARY",
"auto_increment": true
},
{
"name": "username",
"kind": "VARCHAR",
"length": 25,
"default": "NONE",
"index": "UNIQUE",
"auto_increment": false
},
{
"name": "name_last",
"kind": "VARCHAR",
"length": 25,
"default": "NONE",
"index": "NONE",
"auto_increment": false
},
{
"name": "name_first",
"kind": "VARCHAR",
"length": 25,
"default": "NONE",
"index": "NONE",
"auto_increment": false
}
],
"data": [
{
"id": 0,
"username": "Neat-O",
"name_first": "Kenny",
"name_last": "Hill"
},
{
"id": 1,
"username": "12thAggie",
"name_first": "Reville",
"name_last": "18"
},
{
"id": 2,
"username": "I_Like_Cheese",
"name_first": "Shh",
"name_last": "Secret"
}
]
}
With this file I need to be able to read in and essentially create an object in C++ representing this table, or any table in SQL for that matter. It is a limited implementation of SQL, so let's just consider this markup to hover around the edge of the intended functionality. In my current design I am thinking it would be best to define abstract column objects, that can essentially be stacked together to form a whole table. Operations can be performed on all the columns as though they are a whole table, and then saved back to disk. Again, I am not concerned with performance at the moment mostly readability and implementation. So my question to you C++ gurus is this, how would you interpret this data and manipulate it once instantiated as a C++ object? I have been exploring generics but I keep getting hung up on the "selectable" data types, INTS, VARCHAR, etc... My current class "kind" (for a column has the following members:
template <class T>
class Kind
{
private:
int length;
string kind;
string default_value;
string index;
int auto_increment;
vector<T> data;
}
However, when trying to create the table I would need to somehow create a type that allows for multiple types of generics.
vector<Kind<?>> table;
Where allows for VARCHAR, INT, etc... Any help with this would be appreciated! Thank you.